Yes there will be corrections due to the finite size of the nucleus, the Bohr-Weisskopf effect will occur, due to the fact that the hyperfine field due to the electrons is not constant at the nucleus position (the electrons can be outside the nucleus to generate a B-field inside the nucleus)
After having read some other answers I am confused, someone says that there is no contribution due to the fact that there is no overlap, I understand that argument. However I do not understand why the Boh-Weisskopf effect can only occur if there is overlap? To me it looks like this effect is independent of the overlap?