Why did he say this to me?

Hey y’all. Just wanted to vent for a second, and try to figure out why someone called me a name. So today in my costuming class, I had trouble tying a knot with my thread. (They kept ending up WAY too small, so it would go through the hole when I pulled the needle through.) I asked the guy next to me if he got his knot tied, and he said he had. I told him how mine always end up super small, and he said “so are mine.” Which surprised me, so I asked “Is it working?” And he said “yeah, it’s working!” So I then said “what!? Why are yours working and mine aren’t?” (I said it jokingly.) and he goes “cause I’m not a scrub.” (Also, what exactly did he even mean by that..?)
Then, everyone else in the class went “whoa!” And it really hurt my feelings. I’m pretty sure he was joking, but it just put a damper on my whole day.