in addition to the excellent advice above, you might try gloves (thin ones, partially fingered) Sometimes that extra little layer betw. your hand and the paddle shaft will create a looser grip.
The other thing may be a glitch in your forward stroke - specifically if you are locking your elbow or carrying it at an odd angle as you move to catch or retract your paddle. Either may cause torsion & pain in the lower arm.
No way to diagnose this online. Get w. a friend who has a really good stroke or take a lesson or two. No shame in that - the mechanics of a great forward stroke are not intuitive.
I paddled a whole season and some, had arms like Freya's and thought I was doing great. Then took a class focused only on the forward stroke and got schooled. The instructor tore down everything I was doing. Fortunately he set me straight before I had too many bad habits to unlearn LOL.