Blisters are a frequent problem for people training with weights. If the blister breaks, use a sterile scissors to cut off the excess skin flap. clean out the wound with saline solution and cover with liquid bandage to keep clean. Hold a cold can or bottle of water will ease the pain.
Allowing air to get to the wound will help dry it out.
Prevention involves good hand hygiene. Any lifts in the skin can be aggravated by friction as the bar slides in the grip. Use a pumice stone etc. to level out any such lifts. Also use a proper grip. If you take the bar into the base of the fingers rather than the thumb. less movement will occur reducing the likelihood of blistering.
Enjoy your training and remember "Train smart"