So I was cleaning a bc reel and accidentally knocked my spool over, it hit the concrete and now it has a small dent in the ring. Will this effect casting?

How bad is the dent? Can you install the spool and does it spin freely without making contact with the frame?

Probably, but it depends if you notice it.

 

Give it a try and determine if it is detrimental to your use of the reel.

 

If it is, order a new spool.

Man I was scurred, went out this morning and tested it still throws fine. Did not want to fork out another 50 bucks for a spool

Not sure if the lip or the spool skirt was dented.  If the lip, make sure the concrete didn't nick the lip, which can damage the line.  If it did, smooth it up.