When to start scar treatment? (Pics included)

Bones, joints and muscles
1

I recently fell on a run and ruined my knee, I managed to open it up 5 inchs long and around 2 inches wide transverse below my knee, with some neat boney exposure. 

Went to my local ED and they stitched it nice and I'm super happy that scar is quite thin (comparatively), but there are two areas that haven't completely healed in the middle and to the far right, where I presume the cut was nastier. 

Can I start scar treatment on the areas that are healed? (e.g kelo-cote, silicone pads, etc) 

or should I wait until the whole thing is healed? 

Also anyone know what causes scars to widen? I had this happen with a forearm wound and really want to keep this one as thin as it is now. 

2

Let it heal.  What topical antibiotic are you using over the scar?

3

none, I was put on oral antibiotics when it happened, but I've just been told to leave it uncovered and not get it wet 

4

What antibiotics are you on?

5

Finished the course but was on co-amoxiclav