How do I fix this problem with my iPhone?

ah. This has happened to me many times before. If you have a can of compressed air, using it on the headphone jack should do the trick.

If you don’t have compressed air, looks like you’ll be huffing and puffing for quite a bit. Make sure you don’t overdo it and get light headed and drop your iPhone… Believe me I know it could happen. Good luck fixing it!

The only way to fix it is blowing on the headphone jack?

You could also try plugging and unplugging your headphones many times to try and loosen the dirt. Then give it a few puffs of air to get rid of any leftover dirt.

From what an Apple genius told me, there’s enough dirt in the headphone jack to trick your iPhone into thinking that your headphones are still plugged in. I highly advise against sticking anything other than headphones into the jack.