Hi Sudero and welcome to Dhamma Wheel.
As for practicing correctly, it would depend on what you were actually doing when you were averting your attention to the nostrils area. Particular sensations are not indicative of progress nor incorrect practice.
I recommend that you make contact with the assistant teacher with whom you sat your course by contacting the course centre where you did your course,or contacting the course centre who will be able to put you in contact with another assistant teacher who can give you appropriate guidance.
I'm glad you are keeping your practice up.
“No lists of things to be done. The day providential to itself. The hour. There is no later. This is later. All things of grace and beauty such that one holds them to one's heart have a common provenance in pain. Their birth in grief and ashes.”
- Cormac McCarthy, The Road
Learn this from the waters:
in mountain clefts and chasms,
loud gush the streamlets,
but great rivers flow silently.
- Sutta Nipata 3.725Compassionate Hands Foundation
(Buddhist aid in Myanmar) • Buddhist Global Relief