|Not to disagree with Richard59 but I have personally bumped the tray while it was extended and did manage to fix things. |
The tray is off the tracks. You need to get it back on the tracks. This should have no effect on laser alignment.
First you need to get the tray back open. There should be a very small hole just below the tray. Insert a straightened paper clip and push in. The tray should move forward. You may need to help it come out.
Gently lift up on the side of the tray you bumped and at the same time gently coax back in the opposite direction of the original bump.
If you can't feel the problem and want to mess with it then remove the drive and dismantle it. You will readily see what the problem is.
Worst case scenario is that you can't get it fixed. If it comes to that look for new drives at newegg.com. You need to get a drive that is compatible with available connections. The two types are IDE ATA (PATA) or SATA.