iphone 4s has stopped playing sounds after ive removed head phones

Hi, does anybody know how to fix this problem?

i plugged in my head phones and afterward i wanted to play music outloud, this has stopped and when i press the volume buttons the icon shows but does not show the volume going up or down. this is also the case for playing music out loud the volume doesnt show.

if any one could help or has any advise it would be greatly apreciated.

Thanks

Laura.