My macbook air says mac os x utilities when i turn it on

I assume you mean you are booting directly into Recovery Mode and seeing the dialog below:

I can only think of two reasons why this is happening. 1) the recovery partition is the only valid startup partition the computer can find or 2) you've managed to set the recovery partition as the default start partition. Let's hope it is #2.

Restart your computer and as soon as the grey screen appears hold down the option key. After a few seconds you should get a list of bootable partitions and we'll hope there are two. The second should be labeled Lion Recovery (or perhaps just Recovery) and it is the first partition you want to boot with. Select it and cross your fingers.

That shouldn't happen since we know you have one valid partition at least. Try this. Restart and let it go to the Recovery Partition. Then run Disk Utilties and repair the drive. Then try restarting and again press and hold Option as soon as the computer restarts.

You mean it rebooted into recovery mode or the screen remained grey?

Sounds like you need to reinstall the OS. Hope you have a backup.