I think i have injured my penis somehow. when i masturbate or put pressure on the base of my penis at the top side i feel a sharp pain in the inside muscles/ligaments or whatever is in there. i assume i strained it but would like advice please:?

I recommend that you be examined by your doctor to be sure that isn't anything more than a muscle strain. They can check for a hernia or other condition. If it's a strain, you should rest the area and can take ibuprofen or acetaminophen; can also apply warm compresses to the area a couple of times/day.

give it a rest

FIND A GIRLFRIEND TO DO PLEASURE YOU AND REST YOUR HANDS.