Avoid this .to rest and start again gradually. Do hot fermentation

Protein rich diet help for body builders. But there is no relevance in terms of strength corresponding to food intake. We have dominant right hand users in majority, hence dominant hand can do much more than the other side. Finally gym work out, you should do under professional guidance, why because, first of all, you need to decide, whether You want to become Body builder or strength trainer or for fitness, further you need to undergo different protocols respectively. Particularly in your case of 5kg biceps or triceps workout, it should be gradually progressed instead of starting with 5kg,

Chiropractic adjustment will help. Hot and cold pack fomentation.

Have u joined gym for the first time?? If yes then it could be muscle soreness after hitting gym....don't overdo yourself at gym..put ice and apply any gel afterwards and give some break to your left hand....when pain subsides then start with mild exercises....take protein rich diet

Usually the dominant arm is stronger. When training at the gym go with the amount of weight and repetition of the left arm. Do same for both the sides till you increase it. Consult online for further information