I'm a left handed shooter and the safety selector in the left side of the rifle digs into my finger each time the gun recoils. Is it possible to remove the selector on the left side of the gun?

You bet: how much are you willing to spend?

I'm not aware of an aftermarket part that does what you want inexpensively, but a real gunsmith or machinist should have no problem inventing and machining the part you need. I wanted to get rid of the stupid add-on safety my Polish Tok had for much (if not exactly) the same reason as you, and I found a local machinist and told him what I needed. He made it, and it worked. I can't remember what it cost, but it wasn't much. If you do the same, you might not pay much; if you take it to a 'smith and have him do the brainwork on it, it may cost more. Best of luck!

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Now go make God proud...

There are ambi safetys available. Shouldn't take but a couple of minutes to cut the left lever (either off or shorter so it doesn't interfere with your trigger digit) with a Dremel.

If you shop around, you might find a single safety for the left handed. With all the other widgets available for the AR someone has to be making this.

I found out that the colt AR15 lever is ambidextrous, so I bought one and installed it, and it works perfectly. Its also longer than the M&P's which is better for my small thumb.