I would not want to spray AluShield that close to a nostril because she might breathe it in right when you spray it. So to start with, I would do what has been suggested and try to wipe a blob of it onto the stitches. Other than that, if it were anywhere else on the face here is how I would do it, and what I did when my horse needed AluShield on a substantial cut on her face right between her eyes.
Shake the can a lot, right near the horse and facing her so she can see what you are doing. Then hold out the can and spray a little bit, a quick spray, downward between you and the horse so she can see what you are doing. That might provoke a reaction but just ignore her and brush her neck. Brush her neck holding the AluShield can, kind of rub the can on her so she gets used to the idea of the can getting close. Sprits a little bit on her shoulder, then ignore her. You’re done. Every time you groom her for the next few days, shake that can and spritz a little bit somewhere on her body or leg. You will get so you can control the spray and just get a little bit right where you want it.
The first time I sprayed my horse’s face wound I did it quickly with just a dab/spritz and she didn’t like it but I kept on every day and she reacted less each time. I think the noise is what they object to; I don’t think they actually feel the spray, and they get desensitized quite fast because it is a quicker action than fly spray and it doesn’t smell.
If I had to spray near a nostril, I would hold one hand over the opening and do a quick spritz while the nostril is covered. Oh, and spray close up so you don’t get a big cloud of overspray.