What I'd recommend is to add something like this:
Add household ammonia to 50g of tobacco (UTFSE for finding the amounts, look for a post under my nick). Then add enough DCM (~500ml) to soak the tobacco. Just let the mixture sit for a while (magnetic stirring or occassional shaking is good).. whatever is most convenient.
Then strain the mixture with a metal strainer, then with a cloth over the metal strainer. (*) Extract the nicotine in DCM mixture 5x with acidic brine. (this means saturate a reasonable amount of water (~500ml) with salt, then add a bit of HCl) (when you do this, you will notice that the brine solution no longer smells of nicotine, I think it starts to smell sort of like tea) Recycle your DCM by distillation. Once you have your brine, basify it with sodium hydroxide and extract with the recycled DCM 5x100ml. Fractionally distill off that DCM to get good quality nicotine freebase. Assume ~50% recovery of the ~4% nicotine content of tobacco, and dilute it with distilled water. (don't try to simplify this method! you will get nasty emulsions!)
Then use that for a nose spray. It burns and likely will bring a tear to your eye, but it works. Use the freebase, not the salt.
(*) if you want, you can stop at that point and simply distill off the DCM, and dissolve the crude dark brown nicotine into water. Unfortunately you will get a really bad emulsion form (the waxes/fats/whatever don't dissolve into the water, they must be filtered) when you add water to make the spray. This is what I did the first time with this method... so despite the loses, I recommend doing the A/B, you get an almost colorless nicotine freebase.
Btw, determine the properties of your nasal spray by filling it with water, then pumping out 10 or so pumps. In 10 pumps, the one I used went down 1.0g on my scale. So each spray adminstered about 100µL per spray each of which I decided would contain 5mg of nicotine. (other people found this to be too much as it would give them nausea)
Be careful not to OD on nicotine, it feels like you're going to die, similar in ways to a PMA overdose. (doesn't last long, stomach upset, intense, not really "high" per se, etc)
