Have it checked to be sure. You said you have had sex in over a year? Did you mean you 'haven't had sex in over a year'?
A blister like that could be just a pimple, but, not to scare you, is also a sign of syphillus. Though the lesion from syphillus is useally tender and hurts to touch. Also, after the lesions "pops", a hard scab forms.
It never hu...
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