First of all I would like to thank who ever can answer this for me...

The hot water valve under the bathroom sink is leaking from just behind the valve knob... or it could be from the nut behind it... how can I stop it from leaking... everytime I turn the valve on it starts spraying and dripping... thanks again for anyone who can help

Canuck74- try to tighten the large nut right behind the turn off & turn on knob,use two (2) pairs of channel lock plyers, turn clock wise to tighten, If this don't help , replace with a new shutoff valve. I always checked these nut even on new shutoff's because I have found them loose from the factory. Have a good day & GOD BLESS ::: Hope this helps, if it does rate my ans. Below:::: F.B.E.

I think it might be a good idea to turn the water off at the water meter, crack a hot water faucet open to relieve pressure from the hot water tank, and replace the valve. They are inexpensive and I would use a 1/4 turn ball valve as a replacement. If the new one uses a compression fitting, be sure and clean the pipe well and check it for any damage or flat spots.
A dent or flat area of the pipe is very hard to seal with the fitting and may even be a cause of your problem. Good luck with it.

First of all i would like to thank who ever can answer this for me....

the hot water valve under the bathroom sink is leaking from just behind the valve knob...or it could be from the nut behind it....how can i stop it from leaking....everytime i turn the valve on it starts spraying and dripping...thanks again for anyone who can help
If the stop looks like this,(see image) then it's a simple repair.
Open the valve up until it begins to leak past the bonnet packing nut.
Now just snug the nut up until the leak stops. Do not over tighten. Good luck, Tom

It depends what kind of valve (angle stop) you have. . I assume it is type of valve shown in the response above. It may be only loose "packing nut" that is located directly behind the handle. This nut usually leaks when valve is operated after long time in use. Packing hardens around the stem and looses its seal when valve is operated. Take pliers and give it 1/4 turn. The leak should stop.

I know Canuck74 resolved the issue... but here is a picture to compliment everyone's answer!

See below... ;)