The meaning of the term "怒る" does not change when pronounced differently.
In general, we use the sound "おこる" more often when the term is used as a verb.
The sound "いかる" usually appears in a derivative noun "怒り(いかり)" (=anger) or
in a few idioms such as "怒り狂う(いかりくるう)". After all, I would suggest you to
use the sound おこる except for these two examples.