Dogs nail is curling, how can i cut it?

i have a chihuahua, he is fairly small but not too small, i never worried about his nails as they naturally grind down with the walking. recently i saw that his "doggy thumb", the small nail beside the paw is beginning to curl, its already done a 360 spiral and its starting to spiral a bit more. i recently cut his other nails and ive been trying to cut that nail because i dont want it to hurt him but he cries everytime as soon as i place the dog clippers on the nail. i apply a bit of pressure and he starts crying and its worrying me because i dont want to break his small paw on accidient and i dont want to have to take him to the vet over something so small. his grandpa has a nail grinder but im not sure if ittll work on him because its already curled and i dont want to hurt him. so what can i do? just deal with his screaming and clip it away and get bitten or just take him to petco or the vet?, i also want to know if the grinder might work because going 40 miles just to clip his nails is a bit costly. help please. also do you have any tips on how to clip the small nail without it being painful. thanks!