Hi there Alex.
From your history it is clear you had a 'sore' that got worse after sex.
But, did it appear after sex in the first place?
Yes it does indeed appear that you are allergic to 'Neosporin' & that could have worsened it!
However, the ulceration earlier worries me. Was it tender? If not, please get a
VDRL test done.
Once you do the test, please start yourself (in conjunction with a
dermatologist on the ground) on a course of antibiotics.
Locally, do apply a cream with betamethasone+
fusidic acid twice/daily for 2-3 days & then review the scene!
Always practice
safe sex young man even if with a regular partner; Abstinence for a week till this all heals is prudent!
Cheers & wish you good luck & great health!
Dr Praveen Rodrigues MD
Dermatologist & Venereologist
Vikram Hospital, Bangalore, India