Thanks for your question and concern. Firstly, I would suggest you to try yourself to ease the foreskin of you penis back very slowly and gently. You can try this while taking bath with the help of some good soap. If you find it very painful and the problem still continues, then you should probably consult with your doctor. It is difficult to predict the issue from the given description but it can be one of the STD symptoms. There are different types of STDs spreading these days and it can be one of them though it is really difficult to bring any conclusion to it without testing. So I would suggest you to get your checkup done with the doctor ASAP. Feeling nervous is quite common for you but you should always remember that maximum numbers of STDs are curable these days with the help of various treatments and medications. Delay in the treatment can cause the problem or the infection to grow further and get worse with time giving way to various other problems. In case you are extremely worried about the STD symptoms then you could probably visit the GUM clinic and get your test done along with various sessions on the STDs cure and precautions. GUM clinics are usually present in the local hospitals and if you don’t want to visit that then you can also visit a separate GUM clinic. The GUM consultations are provided totally free of costand the information about you is always kept confidential. You should always use condom during sex to avoid the different sexual infections caused by the unprotected sex. Best wishes.