It's really easy to undo the PS2 and have a look at the lens (and clean it with a brush or something). At might just be dirty.

Turn it upside down with the front towards you. Renove the rubber/plastic screw caps.

Undo the middle and right rear screws and the 4 screws on the lip/rim below.

Turn the PS2 right way up and gently remove the lid from left up to right. Watch the cable that comes along with it.

The DVD-ROM will be on the right. Remove the small screws on top and the small screws on the rim below and wiggle the cover off. You'll see the drive.

Clean the lens; check that otherwise it looks OK. Recalibrate it if you want to! Put it back together and try it again.

There is a small chance that it'll work because it plays one game at least.

What else? Take it to a PS2 repair centre.