My manager mocked my stutter tonight

My manager mocked my stutter tonight I’ve had a stutter since a massive mental breakdown in July last year that landed me in the hospital. Since I’ve come back to my job I’ve had the stutter mostly under control, however, occasionally it pops up. Tonight when my manager asked me what time I was leaving I stuttered trying to tell him 9:45. I had to heavily emphasize the 45 after a few struggles to get it out. He then said it exactly the way I did like it was a joke. I’m sure he didn’t mean it as an insult to me, however, it’s now made me even more self conscious of my stutter.