If I chipped my tooth will it decay because I hit my front tooth and chipped it?

Generally speaking a chipped tooth must be treated immediately to prevent further fracture, tooth sensitivity or possible root canal treatment.
Chipped tooth does not cause decay, but if remained untreated for a long time, it can cause decay depending on how much dentin was exposed.
See your dentist or a dentist nearby to restore your tooth immediately.

-- 
Dr Anthony Mobasser 
Reconstructive & Cosmetic Dentistry
9201 W. Sunset Blvd suite 618,Los Angeles Ca 90069
P : 310-550-0383