Speaker muffled

I’ve had an iPhone 11 since November, and the sound worked perfectly until earlier today. After a run, I disconnected my AirPods and continued listening through my phone speaker. It sounded quieter, and a little off tone. I began doing basic tests like turning the volume up and down, which worked. I held my finger over the speakers, and discovered that one of the bottom sets was no longer playing music. How, if at all, can I fix this?