Welcome to icliniq.com.
I understand your concern.
This is looking like ulcer. It could be herpes or other STI (sexually transmitted infection). Do a human papilloma virus (HPV) test and avoid sexual activity untill you complete your medicine course. Use a condoms while having intercourse and do not worry it could be because of some minor infection also. Even if it is herpes it is curable with proper medicine course but before going towards any treatment we should know which infection is this. To avoid such subsequent infections, use condoms while having intercourse, keep genital area clean and dry, change undergarments twice a day.
I hope this information helps you,