What could be the explanation for these odd symptoms on my right arm?

So for the past two days I’ve had a very strange feeling on the underside of my right arm (the smooth part without the hair). It feels very sensitive. If anything touches it, it hurts, including water. Washing my hands is now a painful experience. There is no redness or any swelling visible to me.

I was doing some yard work the other day, though, and I was thinking maybe I could’ve been bitten by something or somehow been exposed to a plant-related chemical. All I know is that it’s been going on for two days and it’s really annoying. The pain is strongest right under my wrist. I was even thinking carpal tunnel syndrome.

What could explain this?