What Causes Pain In Urethral Opening While Passing Urine?

Hi, I was recently diagnosed with several UTIs, and got treated for them.

However, since I have finished with the antibiotics (about 3 weeks ago), i have

still been experiencing a slight sharp pain in the urethral opening every time i

urinate. I got checked out, and the tests for infection came out clean, but

apparently i have a very small "nick" in the urethral opening. Could this

explain the slight pain after urination? it only bothers me for about 15 mins

after, especially if I "push" or clench the muscles in the area. How long would

this take to heal? This all started after having sex with my boyfriend, who is quite large.