Reseal under edges of all three shingles.
How to repair a 3 tab shingle roof.
However if that is not a possibility then your second best option is to find rolled roofing once called 90 lb.
Remove an undamaged shingle from the roof and use this as a pattern to cut new shingles from the rolled roofing.
Removing 3 tab shingles using a flat bar to do a repair.
The best way to repair a t lock shingled roof is to have it replaced typically this will be covered by insurance.
Then push the pry bar under the shingle directly above the damaged one and remove the second row of nails the same way.
Press tabs down into the cement firmly and secure the shingle into place.
If there are nail heads that are not currently covered by anything if multiple rows removed then create new holes in the roof to hold the shingle by moving the nails over.
Make sure it looks right and lines up properly.
Removing 3 tab shingles using a flat bar to do a repair.
Slip the pry bar under the damaged shingle and pry upward.
Once the nail pops up about 1 4 in remove the pry bar press the shingle down and pull out the nail.