Turn up volume it says headphones

I've come across this issue a few times, and most of the time it is one of two things, so check these out:

Look inside the headphone jack and make sure it is decently clean. Sometimes junk inside can cause the device to think headphones are plugged in when they aren't. I'm pretty sure you would know if a headphone jack had broken off inside.

Also, check for water damage around that flex and surrounding area. Corrosion can cause the device to assume there are headphones plugged in also.

Good luck!