Is this tissue nercrosis? Should I be concerned? I had dermal filler in my nose 3 days ago (photos)

Since you had a bruise after your treatment, in the same area, that small lump could still dissipate with time, as this may simply be a bit of residual bruise that needs more time. I hope that this is helpful! Sincerely, Dr. Joseph

This looks like bruising, which can be typical. Icing and arnica may give improvement. If you remain concerned, I would follow up with your injector. Hope this helps.

The photograph shown looks like a bruise.  When using a cannula, bruising is rare.  When using needles, bruising and the risk of necrosis is much higher.  I don't think this is necrosis but if you're concerned, then follow up with your surgeon. 

Dear Sydney,It appear to form your photo to be normal bruising but as the previous physician stated, if there is pain, its important to return to your injector immediately. Pain can indicate necrosis and can be treated with hyaluronidase if a hyaluronic acid was used in your procedure.Best to communicate with your injector about your concerns.I hope this was helpful. 

Hello,
From the pictures you have posted, it certainly looks like a bruise but I am always very careful with noses after dermal filler, so if you're worried you need to be seen by your doctor again. Safer to be seen and reassured, than be worrying. 
Necrosis is typically associated with pain, altered skin colour and the appearance of pimples.
If in doubt, get it checked out.