Bear in mind that I've never had to use a stick, I'm extrapolating from the aches caused by gardening tools. And assuming that Avon's hands haven't been hardened by manual labour.

Until he becomes accustomed to it, the palm of his hand will become tender where the pressure of leaning on the stick falls. If the stick has a knob then it will be in the centre of his palm, if a handle, then further towards the heel of his hand. As he pushes down on the stick to support his weight the tendons in his forearm and his triceps will be working more than usual to hold his arm rigid and the ache will go up into his shoulder as well.

In fact thinking about it, entropy_house will be just the person to describe the aches and pains. Other than the twisting motion, using a screwdriver will be acting on all the same muscles.