I feel your pain though mine was the front screen only. If you want to keep this phone (& believe me I couldn't get excited to get anything else available), two options, call LG (800.793.8896) & they'll ask you to send your phone in for $ repair estimate &/or send it to any of various places which offer the fix-up service (google "nexus 4 screen repair"), prices raging from $160 to over $200 for the front screen, you can assume + more $$$ for the back one.
I went w/ the latter rather than sending it to LG - in light of commentary on this & other forums (long delays &/or absence of tracking)....I used iResQ, very quick response & very happy w/ the service - in 4 days I had my phone back, perfect.