OCD and fear of getting sick

Hey guys I'm new to this whole thing so I apologize in advance if I'm somehow doing this incorrectly. So today I was at the DMV getting a new license and the man before me in line was bleeding. I was unaware of the fact that he was bleeding until after I had placed my arms on the counter where he was standing. After I leaned on the counter the woman behind the desk told me that the gentleman before me was bleeding and that I should look to see if I saw any blood. I did not see any blood, but I did notice a brown spot on my finger. I couldn't be certain what this brown spot was, it didn't seem like blood to me. It looked like food or something. Nevertheless, my OCD runs with uncertainty like this and I am now convinced that I have contracted HIV. For what its worth I have a small cut on my thumb (when I say small I mean it has never bled and it is a slight blemish on my skin) that could possibly serve as an outlet for the virus to replicate. Needless to say I returned home and changed my clothes and showered. Should I be worried? Should I be tested for HIV? I know this is my OCD and I know to os probably a bad thing to be searching for reassurance but I can't help myself.

Thanks in advance

I don't think you have anything to worry about. 1. It doesn't even sound like it was blood (not red) 2. I don't see how that blood could have gotten into this tiny area on your finger that has never bled 3. I don't think it's that easily transmitted. 4. that guy probably didn't have anything wrong with him. worst case scenario, you get tested if you can't stand not knowing