They actually sell cleaning cd's. It has a fine brush on it designed to clean off the laser.
They used to sell them everywhere. Now, who knows. Find a music store that still sells CD's and see if they have one.
If that doesn't fix it; check CD's and then finally if that doesn't resolve it then it is the unit itself. The skipping is stopped on automotive units by a combo of buffer memory and agitation isolation of the laser and unit.
