[thanza]

So after cleaning my bike I went to give it a quick ride to insure everything is fine and on the second to last sprocket on the cassette it sounds like it is grinding and also noticed my rear wheel is untrue is this a big problem?

 

[Racebike]

Check so you don't have any dirt or small stones in your cassette, also check that specific cog for any damage.

Your wheel should be straight, true it or visit your LBS to get the job done.

 

[zebrahum]

That is probably an adjustment issue. Might want to have a LBS take a look to make sure the hanger is straight. You can check by putting the rear shifter in like third gear, then standing behind the bike and seeing if the two jockey pulleys on the der are lined up exactly with the cassette. If it's off even a few millimeters it's possible that is what's causing your trouble. Other cause is a simple tension adjustment of the rear der.

The trained eye of your LBS (unless they suck) will be able to fix that problem within minutes.