Why is my sound blocked on my iphone 4?

I can hear music and sound when earphones are plugged in.
I can hear my phone going off
I can hear my tones and stuff.
I can't hear music out loud on speaker.
There's no option to turn up the sound on the part that slides up (on ios7)

Yesterday it had a bit of water damage. My friend fixed it and I just took it off of recovery mode but this is the only thing wrong with it. It's not on mute. I'll fiddle with mute off and on and it will come up as normal but when I go to turn the sound up or down there are no sound bars. It just comes up as ringer. How do I fix this? Do I have to get it repaired professionally?

I had the same problem with my iPhone 4.
The bottom speakers sucked completely. The one on the left didn't work at all an te one on the right had muffled sound. I could not fix the left but I did improve the one on the right this is how;

Step 1: Baby wipes- If you have baby wipes go to step 2 if you don't go to step 3
Step 2: Simply wipe off the speaker with the baby wipes then dry the speaker quickly with soft toilet paper, this should improve sound somewhat. If not satisfied then take case off and unscrew the back, the speaker might be misplaced. If so set it back.
Step 3- Wet a paper towel, not drench just make it damp. Wipe speaker and then quickly dry. Still not satisfied? Unscrew the back, the speaker might be misplaced. If so set it back to proper position.