Breast Reduction 5 Weeks Ago, Nipples Look Flat?

Without photographs it's difficult to say where you are in the healing process. I can't say in general there takes many months for the surgical sequelae of a breast reduction or breast lift to reach maturation.

When the nipples are totally removed and replaced as a nipple graft, it's very common and normal for what you are describing to happen, since the surgeon has to remove some of the tissue from the nipple with this technique.  Once things are healed, a little injectable filler in that area can help restore the volume.

 

All the best!

This is a problem with a free nipple graft.  The nipples tend to look like they are pasted on.  After your are healed there may be some minor things than can improve the appearance of the nipples.  

When the nipples and areolas are removed and replaced as grafts, the nipples almost always lose volume and definition. Once healed your surgeon can offer options if the appearance is not satisfactory. All the best.