Hi Twinkle,
I've had lymphoedema since March, and am only recently coming to terms with it. Such a shock! I, at least, should have been expecting it, since I had node clearance, but I have learned that many, many women with only one or two nodes removed go on to develop lymphoedema.
Yes, it is quite normal for your arm to ache and even hurt, and to feel cold (especially in this weather).
First of all the important things to do right now are: elevate your arm (between waist and shoulder height not over your head) as much as possible. Drink drink drink water. Hydration helps lymph flow. It will help if periodically you can raise your arm above your head and clench and release your fist ten-twenty times (slowly, it's all about helping sluggish lymph move OUT of your arm). Deep breathing from the diaphram (fill your lungs) also helps get this lymph moving. It helps if you stroke your arm (which feels ridiculous) again slowly and someone told me "like you're stroking a kitten". Do your hand, then your arm in bits (maybe four or five) coming up over your shoulder at the end.
There is a really great US website called Step-up, step-out (google that plus lymphedema and it'll get you there) with a lot of amazing help. The Lymphoedema Support Network (lymphoedema dot org) is also good, although not a patch on SUSO. Finally there are some really amazing women on one of the US forums "breastcancer[dot]org" where if you search on lymphoedema you will find a real wealth of practical information and real experts who can answer your questions cheerfully and quickly.
Finally, the big thing to be careful of is cellulitis. Start being careful now. I have antiseptic cream & spray in the bathroom, the bedroom and my handbag. The smallest cut, bug bite, or hangnail can allow infection into your arm and the stagnant lymph provides a perfect culture for infection to grow. If you do get a cut or bite, apply antiseptic and WATCH it. If it seems to be becoming infected do not wait--go to the hospital. If you feel like you are getting the flu and your arm becomes warm or hot--same thing--go to hospital. Cellulitis unchecked can lead to a long stay in the hospital or worse, and every incident of cellulitis makes the lymphoedema harder to control.
It all sounds really overwhelming, but hang in there--it is both manageable and bearable.
Quail