Car will totally compensate for 87, just will make less power as it will pull timing, but won't cause damage, just run it and get some 93 when you can. Also, do not go to autozone and buy octane booster and dump that in - that potentially is much worse than just running the straight 87.
All dealer loaner 335's get 87 all day long everyday as no one pays the extra to put 93 in them and they all survive just fine!
2008 E93 335i, GIAC Stage 2, HPF IC, Injen Intake, Defective AR Design DP's with useless cats
2014 X3 35i JB Stage 1, 2011 Audi S4 Giac Stage 2 + DSG Tune