so i was in the sun for not more than 15mins, and i was wearing a white shirt and an hour before i applied lotion to my new tat!…could my new tat get effected by the sun?

And after 3 weeks how can i protect may tat from the sun? Can i just apply sunblock of spf 50 or more, or i have to do something else couse i heard that a tata is fully healed after 3 months!