It looks like guava fruit fly damage. The adult female flies lay egg just under the skin of semi repine fruits. The maggots develop and feed inside the fruit, causing the flesh to turn brown and soft which emits foul smell. This damage also act as entry site for fungal and bacterial pathogens. After maturation, this maggots fall out and pupate in soil.

Management:
1. Collect the fallen fruits and destroy them.
2. Also you can harvest fruits early to reduce flies damage .
3. You can use traps to monitor fruit flies. Traps can be purchased in the market or you can prepare one. Take plastic container with lids (one quarts yogurt container is fine). Drill holes (10 to 16 holes) that are 3/16-inch in diameter around the upper side of the container. Add 1 to 2 inch of pure apple cider vinegar (not flavored one) and a drop of unscented liquid dishwashing soap into the container. Hang the container in shade near trees before fruits ripening and check the traps frequently for flies. You have to change the vinegar every week.
5. Spraying protein bait under leaf surface attract flies to single spot which make easier to kill them.
4. If infestation is severe you can spray suitable insecticide like fenthion or dimethoate.