Yea definitely worth fixing the screen, I broke my phone too and was considering selling for parts, but after looking into it it's definitely worth fixing.
Selling for parts will get you around £45.
Screen replacement part on ebay is £37.99 - this is the one I bought: http://www.ebay.co.uk/itm/1710627475...84.m1439.l2649
Selling used nexus 4 will get you around £140 +
So assuming you fix it yourself, repairing the phone will add £100 to the value. Minus the cost of the new screen, that's still around £60 you've gained by fixing it - as well as being able to actually use the phone until you want to upgrade.
CWM Touch Recovery