Inflamed penis... help please

I noticed a couple of large inflammations on my penis early this morning, about 16 hours ago, after I had finished masturbating. One was on top of the shaft and one was on the bottom; both were near the head. The inflammations were not painful or itchy at all, they just look very strange.  They are about as wide as a quarter and are soft to the touch.  And I'm positive it's not an STI because I've been tested since I last had sex.

I searched the web a bit about this and it said this can happen from masturbating too vigorously?  That is probably what caused mine, considering I masturbated fairly vigorously for about 4 hours.  I definitely plan on abstaining from masturbating for at least a week, until these go down.

Has anyone ever experienced these? Is the inflammation an edema or something else?  What are the chances of this happening again the next time I masturbate/get an erection/have intercourse?  Basically if anyone could give me any info on this I would appreciate it.  I've had some ice on it for the past hour but it doesn't seem like that's done much.  Also I'm a healthy 23 year old if that matters.

Thanks.