Yeah, likely a nerve.
And FWIW, I've been a nurse for 21 years and 99% of the time, in my experience, patients HATE hand blood draws. They hurt more than median cubital sticks. However, *I* generally stick where I know I'll get the best chance to hit a vein on the first stick. However, I work in the ICU and do part time at our cancer center: 2 places where people have the most difficult veins to start with (due to harsh treatments or just being super ill or getting stuck all the time).