Rule 13.1c says that you may make two kinds of improvements on the putting green.
You may remove sand and loose soil and you may repair “damage”
Damage on the putting green means damage caused by a person or outside influence such as:
- Ball marks, spike marks, scrapes or caused by equipment or a flagstick
- Old hole plugs, turf plugs, seams of cut turf and scrapes or indentations from maintenance tools or vehicles
- Animal tracks
- Embedded objects
Damage on the putting green does not include any damage or conditions that result from:
- Normal maintenance, aeration holes
- Irrigation, rain, natural forces
- Natural surface imperfections (weeds, bare areas, diseased or uneven growth)
- Natural wear of the hole
And remember, you also get to repair the actual cup/hole if it has damage as described above.
Learn what happens if you accidentally double hit your ball.
Check out more on the new putting green rules at USGA.org.