The fact that your problem started after burning a DVD is purely coincidental. The only correctable possibility that comes to mind is that you need to clean your lens. Run a CD/DVD Cleaning disc (The kind with the tiny brushes) through the drive 3 or 4 times.
Failing that, you might try opening up the drive and carefully (extremely!) cleaning the lens with lint-free swabs and pure isopropyl alcohol or lens cleaning fluid. Do not use Q-Tips or cleaning fluids not designed for lenses. Either would leave more behind than they cleaned off.
Worst case, get a new drive. Your laser may have just expired.