You've had a one night stand with a friend and are now worried that things will get awkward. This doesn't have to be the case. Nor does it really have to turn into a casual relationship. What this turns into will depend on the steps that you take next.
I'll split this into two sections. The first is if you want to turn this into a regular casual relationship and the second is if you want to go back to the friendship you had before.
What to Do to Turn It Into a Casual Relationship
Start with morning sex
This is the best thing to help turn this one night stand into a casual relationship. You want to leave the woman knowing that you can satisfy her every sexual need—and this is exactly the reason she'll want to come back to you in the future. So, a good round of morning sex to remind her of the night before is an excellent idea.
The morning sex will also give you an idea if she's open to a casual relationship. How much does she give back and how much does she take? Is she receptive to the idea of more than a one night stand?
Keep the communication open
While you don't want to seem too eager, you also don't want to leave it too late to text her after the night. About 24 hours is a good guideline is a good time to text her about the great night you had and that you'd like to do it again sometime.
Make sure you keep the communication open and make it clear that this is as casual as she wants. You'll get an idea of how open she is by her responses. If she's not texting you back within 24 hours, she's telling you that she's just not that into you. The only time she might not text back is if she's going to see you soon with others.
Be flirtatious but not clingy
Women who want casual relationships want to feel like you're interested but not overly invested. Chances are she doesn't want you with her 24/7, but she'll want the odd text and want to be flirty around her.
When in a friendship group, keep the flirty to a minimum. She may not want other friends to know that this is turning into a casual relationship as it can disrupt the group.
What to Do to Turn It Back into a Friendship
Discuss it in the morning
Don't be afraid to bring up the one night stand the next morning. In the light of day, things can look very different and you'll want to make sure you're both on the same wavelength. Discuss how you can keep things as normal as possible afterwards. The more awkward you make this point, the more awkward it's going to be afterwards.
Don't forget to call and text afterwards. She'll want to hear your voice to know that this isn't awkward and this isn't all you wanted from her.
You'll want to discuss what you can and can't bring up afterwards. This just helps to set some ground rules you're both comfortable with.
Don't kiss and tell
Don't talk to your other friends about this. Telling others what you got up to in the night and with who will lead to awkward discussions and knowing looks at the other party. It's not fair on your friend and will instantly lead to you being blocked on social media and by text. This intentionally makes things awkward.
The best thing you can do is keep it to yourself. This makes it clear to your friend that you do just want to move forward with just the friendship.
Don't bring it up again
The only time you want to mention this to your friend again is if there's an STI to bring up. Never accuse the friend of passing it to you, even if this did happen. Just keep the conversation open and make it clear you're thinking of her health.
Do not ask your friend if you should get tested! If you think this may be something you need to do, go to the clinic and keep it private unless you need to tell her. Asking her is a sure-fire way to end the friendship as it shows you don't trust her.
Do you want your one night stand to become a casual relationship? Keep communications open and discuss together where this will go.