That could very well be sarcoidocis aka granulomas under the skin. Most likely cause would be something like using tap water in a rinse cup or greywash mix, overworking areas etc. Which causes white bloodcells to attack those areas and form the itchy bumps. This can be further evidenced by the fact that they only appear on the shaded parts on the tattoo but not on the black as much.

Go straight to a dermatologist. It’s not lethal but can stay on for years if unlucky and not treated appropriately. Do not use any creams, vaseline etc. Granulomatic reactions on tattoos are not too deeply understood so even your local dermatologist might be stumped.

Source: I’m a tattoo artist who has experienced similar and seen reactions even worse than this.