Go to an adult store and buy lube to use during masterbation. If it is safe during sex then I would bet it is safe for masterbating. They make water based lubricants.
I am going to be rather frank in this comment. It is a rather frank topic after all and we might as well not pretend that people don't masturbate.
This also happened to me recently. I woke up, went to the bathroom and urinated and at the end of the urination came what was obviously slightly diluted lotion from masturbation. It burned and my penis was sensitive off and on the whole rest of the day. I assumed it all started because I had switched lotions a few days (or weeks) before; this lotion was much more efficient however it stung slightly after I ejaculated. This only happened the one time and I haven't used that lotion since.
It got me thinking though. What if this happens all the time, lotion entering the penis during masturbation, and the only reason it had become a problem now was because the lotion was slightly irritating and my body had just rejected it.
It makes me afraid to masturbate with lotion at all. I really don't want lotion to build up in my urethra or bladder or who knows where... Does anyone have any insight into this subject?? Any comments are appreciated thanks.
Just keep peeing. Unless the lotion was very harsh, it should all come around to normal very soon. Drink a lot of water so you can keep passing liquid through the urethra.