Thanks for posting your query at DoctorSpring.com
I can understand your concern.
From the picture it seems to be a wart. However, since doctors have examined you and opined that it's not a std, i would suggest you visit a dermatologist.
At times just seeing a lesion in the picture is not enough to confirm the diagnosis.
The treatment for a wart would be application of Aldara cream. You will need a prescription for the same.
Please let me know if you have any queries.