By the book, no.
The rules are of permissive nature: they tell you what you can do. What they don't tell you can, you can't.
Similarly to spells, skills, metamagic techniques, technomancer complex forms et cetera once you have an ability, you can't choose to forgo it in order to spent the karma elsewhere, not even on another similar ability.
But in no way you're limited to what you have already chosen; adepts can initiate and increase their magic, which gets an additional power points (quoted from errata):
If you’re an adept, you get a free Power Point whenever you increase your Magic attribute (though this doesn’t apply to mystic adepts, and you can gain a Power Point through Initiation (p. 324) instead of gaining a metamagic.
If you are ultimately unwilling to retain those powers that you deem unnecessary, take this matter to your DM. Maybe he will allow you to retrain as an exception for inexperienced player; maybe he will offer you a metamagic technique allowing retraining (which is a powerful option and one should expect it to be difficult to obtain). In fact, "definition of self changes" is quite in line of initiating and metamagic, so that may be the solutuion.