If your spool is a yellow DMC spool this can be patched with Plasti Bond compound or Araldite available from your local hardware.

Slightly over fill the chip and allow compound to set then sand back to shape with very fine sand paper (minimum 240 grit) or file.

Bakelite spools can be patched with Araldite using the same method and you may even glue a broken section back into the spool.

Later spools are injection moulded and any rough surface areas can usually be sanded back to be smooth or again use Araldite if required.