4 letters:
ikle

5 letters:
knipl, mikel, nycum, pikul, wikel, nicol

6 letters:
bickel, bickle, dickel, fickel, fickle, hickel, hickle, mickel, mickle, mikell, nibble, niccum, nichol, nickum, nicolo, nicols, nipple, pickel, pickle, rickel, sichel, sickel, sickle, tickle, nickel, nickle, nickol, nikkel

7 letters:
bickell, knippel, knipple, knittel, knittle, knochel, knuckle, nicholi, nichols, nickels, nickles, nickols, nicolau, nicolay, nicolls, pickell, nicholl, nickell

8 letters:
nicholls, nichols', nickel's