Hi. Don't try cutting his nails ... if the paws are swollen (possibly due to infection) it will be extremely painful. Leave the nails until the infection has been treated and the swelling has gone down. You really do need to see a vet over this.
Tony
Hi there, It seems a bit strange for the two back paws to be swollen, could it be an allergy that has caused the swelling, you could give your dog an anti histamine tablet, it will be ok to give your dog the ones you get for humans. I hope he hasn't come into contact with a poison of some sort as this would make him salivate and lick his mouth a lot. You may have to get him to the vet soon. Hope he is ok.