Collagen dressings are better than the routine dressings, but should only be done over non-infected wound otherwise it will be a waste.
Secondly, they are slightly costly than routine dressings.
If the burnt area is already showing some healing, you can continue with routine dressings (use ointment megaheal). Else if the burnt area is showing slow healing and still is not infected you can go for collagen dressing.
No special diet restrictions needed.
Next Steps
post some pictures of wound.
Health Tips
limb elevation and high protein diet will aid in healing process.