I recently noticed that I have a bump on the skin of my testicle and was wondering what it is. I haven't had sex in about 8 weeks and this bump just appeared today 
There are several things this can be including - an insect bite, penile cyst, or a blocked skin-pore and you have a build-up of puss causing the bump.
So, look at your hygiene practices, particularly if you have just started doing vigorous exercise. For the lump, I would initially try some liquid antiseptic, rather than a cream or an ointment. Apply once or twice a day and see if this reduces the lump - if it is a cyst these can be caused by severe pressure to the area, or seem to occur on their own - as ever, if you are suspicious of something worse, get it checked by a Medical Professional …