Help, i found a secret phone

My bf and i broke up for a couple months and he went back to his baby mama... weve both made mistakes in the relationship but we agreed to work on us... i got rid of everything from previous relationships that he told me to and ive asked him multiple times if he has anything still of hers, he kept say no but i went snooping and found a phone in his lock box that has provactive photos and videos of him and his baby mama... after this happened i asked him nicely if he had another phone and he said no and told me i could search everything if i wanted to...what should i do