Bubble Thing of the Tip of Penis....

Hello,

i really have given it much thought about it because I never experience pain with it. But on the tip of my penis, on the opening, theres this clearish bubble
, a little under a centimeter in size. On one side of the opening. At the base, you can see like blood vessels. I know it sounds freaky and believe me, i'm freaked out myself. I had this for awhile now, but never gave much thought because I didn't experience pain and never really examined it. Btw, i'm not circumsized, if that helps. Any help would be great, thanks.