If you have a wood chipper, your injured pine tree would make excellent mulch when you take it down. There is no reason to be concerned about using mulch from a recently-felled tree. In the long term, all chipped wood mulch takes nitrogen from the soil as it decomposes, so it's a good idea to sprinkle all of your mulch beds with a slow-release granular 10-10-10 fertilizer once a year to make sure the nutrients your plants need are present.