Also as you don't know much about homeopathy please suck the pillules or crunch them up dry. Make sure you do not eat or drink anything for about 20 minutes either side of taking the remedy. Matrium Muriaticum is a remedy you will be able to get in a Health food shop but you may have difficulty getting the 1M. You may have to ask where you can get it from. Yes you will only need the one dose at that potency (1M). May I suggest you buy a simple introduction to homeopathy as you will probably find it enlightening.

PS I have given this remedy and at this potency to a patient a couple of weeks ago for exactly the same condition! He came out in a funny cold within a couple of days which went away in 2 days. This is the sort of thing that may be initially expected.