After Laser Resurfacing, will skin fill up from within to fill dent like this? How long will it take? (photo)

Often fractionated laser resurfacing alone is not adequate to fill in a dent-like scar as you have.  Instead, I recommend my patients, with such scars, to have subcision followed by fractionated resurfacing.  Subcision is a technique invented by dermatologic surgeons, done under local anesthesia, using a needle or needle-like tool under the skin in the dermis where scar bands and tethers are located.  The needle is moved back and forth gently to break up the scar bands. 

The photo is less than ideal so if is difficult to discuss.  Generally speaking lasers can be useful in treating depressed scars by generating collagen.  There may be alternative methods of treatment or adjunctive treatments needed.  The treatment of scars may  require a series of treatments.  What can be said is that 3 weeks is much too early to know the final result as it may require 6 months or more to see the full effect.  Additional treatments do not usually require the full healing to proceed to the next step.  Several other aspects of scar treatment that you should know:  Rarely if ever do the scars totally go away.  There are many aspects to most scars such as pigmentation, vascularity, hair loss, texture and loss or even gain of collagen and each may require a different approach (laser, injection, etc)