How long after pulsed dye laser can I have Fraxel on a hypertrophic scar on my chest? (Photo)

I had a cystic acne scar on my chest removed surgically six months ago. The surgical scar developed a small hard lump in the middle. I started monthly pulsed dye laser sessions three months ago but after the last session the scar became much more raised. The hard lump is still there. I will have another PDL session in two weeks and would like to have a fraxel session after that. How long should I wait between the two?