Hi Thank you for your query Firstly you should let go of your anxiety. Such a spot appearing immediately after the act may be due to a minor trauma (especially because it was your first time). The color changes are suggestive of some blood collection there. If that s the case it will resolve on its own. The discoloration may take a little while to go but its not a cause of concern. The other cause can be some sort of infection. For the future may i suggest that you totally avoid unprotected sex. It is very important. Well if its an infection it should readily be treated by antibiotics. So don t worry about that too. Consult a dermatologist and he should be able to help you more. Hope that helps God bless you