Just typed out a long response and it disappeared - aaaggghhh - try again.
Hi Blueboo
It sounds like you don't have great support at your hospital at all. I'd suggest that you speak to the BCN about what's happened as she will be able to help you get a quicker appointment. In the meantime, I'd book an urgent appointment with your GP. An open wound means that there is a greater risk of infection and you don't want that. He/she may be able to help speed things up or at least get you referred to the practice nurse (or district nurse who will visit your home) and get that wound cleaned and dressed.
I am alarmed you weren't told about arm exercises. The DVD that Jo has suggested above is very good and will help. Sounds like you could do with some more support though in all ways. I don't know where you live but there are various centres that offer all sorts of help many with centres around the Uk - the Haven, Penny Brohn, Maggie centres (the most widespread) and Macmillan cancer centres which seem to vary in what they offer.
http://www.thehaven.org.uk/
http://www.pennybrohncancercare.org/
http://www.maggiescentres.co.uk/home.html
http://www.macmillan.org.uk/HowWeCanHelp/LocalInformationCentres/MacmillanInfoCentres.aspx
There are also loads of smaller charities that provide support but finding them can be tricky. I also know of the Fountain Centre (based in Guildford hospital) and the Olive Tree Cancer Support Centre in Crawley.
I did develop lymphoedema a year after surgery. but what you're describing could well be just swelling related to the surgery as it's all so recent.
take care and I do hope you've got someone around who is supporting you through all of this.
Elinda xx