Should I tell my bf or no?

So my boyfriend and I use to live together in a apartment but the Lease ran out and we have been struggling which caused him to move back to his parents for a few months and me to move back to mines, I’m 21 and he’s 23. Well, he’s my best friend. I love him so much.. he use to struggle with drug addiction but he got off it and he’s back on them but working on getting off, nobody knows this except me. Yesterday his mom went up to his room while me and him were gone and she found his pills, she’s furious. She didn’t tell him though, but she came to me about it. She went inside his bag and snooped and found his stuff. I’m stuck between telling him that she did that or keeping my mouth shut. Because this will get him very very very heated. I just hate drama and want to keep peace but I feel he does need to know... advice??