i think its the area right above the nostrils that is sinking in a little too much. so the nostrils look really flared out and a bit harsh.
im posting some pics that shows smooth transition from bridge of the nose to the nostrils and the average placement for the nostrils.
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but i know u are probably working form orthographic refs, which is my biggest issue with them, is that thtey only give one perspective, and very linear representation. whereas perspective or overhead refs give better curves and show more movement on the figure.

good stuff nonetheless.