Hello i have a huge problem with my iPhone Please help! (Read Detail please!)?

Hello i just got a free iphone from a friend. He said he jumped into a pool with it and then it went into somthing called single user boot mode.I restored it with itunes and now it is working. but now i see that apple (those Tricky s) put a white dot in your speaker jack i have half a circle and i know it represents water damage but from what i've used so far The touch screen works all the speaker works wifi works fine but have not got a simcard for it. it's an iphone 2g 8 gb and working fine but i dont know how long ago he jumped into a pool with it (i ume a long time ago i think) and im only 14 years's old and i got it for fixing his companys computers because im good with them... will i experience problems down the road with this? or if everythinmg is working it's working right?