If you can't get it wet but you want to try heat, here is a suggestion I got from a doctor while we were on holidays - an improvised microwave travel hot pack.
Get ONE hotel hand towel (or cloth nappy, if you are at home). Wet it, then wring it out. Fold it neatly to the shape you want, put it in a plastic bag of the crinkly plastic variety (like cheap shopping bags) and microwave it for however long it takes to get hot. You may need another dry towel to wrap it in if it's too hot. Be careful to make sure it's not too hot. Apply the 'hot pack' (still in the plastic bag) to the area that wants heat. When it cools you can heat it again. Be careful to not overheat, or the towel will dry out and catch fire. Always check before microwaving, to make sure it's still damp enough.
This way you get dry heat in the area. Not as good as hot water, maybe, but it still might do the trick.
Marg