Question on testicular composition/checking

Hello everybody, something came to my attention today, and I realise I probably haven't put as much thought into it as I should have.

I often notice a strange little grain like lump on the underside on my right testicle when I check. The most bizarre aspect of it is that it seems to move position when I move the skin, nad so doesn't necessarily seem to be located on the testicle? I first discovered it in the March of 2017, and presumed I was pressing some sort of tube or something against my testicle when checking it. For the longest time I just ignored it whenever I checked- thinking it was just that. I ended up checking today and it just struck me that I'm actually incredibly stupid for not getting it checked when it first appeared, and I've since been struck by waves of anxiety, largely over how I essentially left it to sheer luck.

Is this a normal thing when checking? Given I've had it for so long now, I'm not sure of the merit of checking it, but nontheless I think I might go to the Doctor's tomorrow for a long overdue check up. If it was something bad- surely I'd be well aware at this point?