Husband made a tasteless joke in front of his mom

My MIL does not like me. She blames me for my husband having had a drug addiction. I'm 4 years older than my husband. He was 24 and I was 28 when we met. We met at work and I was his boss. It's not a great start I know. I was the manager at IHOP and he was a server. I was struggling with drug addiction and I'll be the first to say I regret everything I did back then. I did invite people over to hang out with me and at my house ask if they wanted to do drugs. Looking back that was wrong. Inappropriate for me to do as a boss. I should have been fired for that. He was one of them and I did start an addiction and we did have a relationship. How our relationship started was messy and we actually broke up and when we got back together we were both clean. My husband is very bad at social cues. He just says things and makes jokes that just aren't appropriate. I think he has undiagnosed autism. Me and my husband are both trying to get into a phlebotomy program and we found out we have to stick each other in class. My husband said "Well this wouldn't be the first time you stuck a needle in me." He thought he was making a joke. My MIL didn't find it funny and left our house and slammed the door. I just feel embarrassed and my MIL already doesn't like me and he makes that joke.