Implant Shifting After Rhinoplasty - Normal?

It can happen. It's not the norm, but if you do enough nasal dorsal implants (of all kinds) you will see, and feel, a shift in some. Consult your plastic surgeon, and don't even begin to fret until six months have gone by. A few reasons to worry would be; redness, fever, purulence, of a general feeling of malaise with an accompanying large watery fullness in the dorsum. 

Unfortunately, im plants can shift at any time. You should see you surgeon to make sure that the implant is not being rejected. Retaping may be in order.