iPhone SIM card problem?

[Cecil]

It says when I start up the iPhone 3GS 16G, SIM LOCKED, Insert a valid SIM with no PIN lock to activate iPhone

Under it, says Unlock, I could enter a PIN...

 

[Necromancer24]

Just enter the pin and unlock it. Did you recently restore your iPhone?

 

[Cecil]

Yes, accident! I bought this iPhone from someone on here...

 

[Necromancer24]

Oh if you just restore it, connect it to iTunes 8 or later and make sure you're connected to the Internet so it can install your new firmware and shit.

 

[Cecil]

Can you go on MSN and help me? Please.

 

[Cecil]

Anoyne? (((

 

[juvenilepunk]

Take a photo and upload it, what Necro suggested should work.
Plug the iphone into your computer, open itunes, click the picture of the iphone on the left tab, click restore iphone.

 

[Cecil]

I can't... It only says on iTunes please enter your pin.