I got made fun of about my stutter for the first time.

I got made fun of about my stutter for the first time. So as the title said I got made fun of about my stutter for the first time. I haven't been diagnosed with a stutter yet, but it's definitely there. I mostly get stuck on words before words and say about 100 filler words, like "So basically", "Ummm", "I guess" and tons more. Anyways I was trying to tell a story at my friends graduation party with a few people sitting down at the table with me. My friend was there along with her sister and my other friend's brother, plus some other people. So when I started the story I was trying to collect my thoughts and said a ton of filler words. He ended up saying "Uhhhh, Ummmm, Yeah, So basically." making fun of my stutter. I have never had this happen. He is really a great guy, but he does make fun of people and it's usually pretty lighthearted. He doesn't really know that I stutter because I try not to around people I dont know very well. He wasn't trying to hurt my feelings or offend me, but still. What do I do about this? Do I tell him that I have a stutter or do I just let it go?