I could tell you that without practice it's not going to be easy. I could remind myself of the same situation. First, I would like to recommend that you should get familiar with the sound frequency of all of the notation unless you clearly can't differentiate the sound of which note or sur had been played. You would probably get more confused, so you may bring the keyboard instrument for that.
Or you could listen to the song with having notation of that song.
For playing those two notes there are only minor differences of blow and if the third finger hole (from the top position of flute) will slightly open/close (not necessarily half) than still. You may listen to Komal
re (if the first three whole blocking sound is
sa for you).
It was a challenge for me to block that hole entirely rather than half open.
I would like to add that if you begin saptak from all holes blocked as
sa then it will be easier to play these notes.
If you don't have a keyboard, and the song you may play is composed within Bhairav, Poorvi, Marwa, (which have komal re) or raga asavari (this has both
You can also search on YouTube to find the composition of this raag.
So keep practicing! If you do, you will surely get success. Hope my answer helps. All the best.