A couple of months ago a small cactus fell over onto my finger. I managed to pull what I could see off the needles out but even now months afterwards it still hurts when I touch the area. There is nothing to see, the finger looks normal.

Does anyone know how long it might take before the pain goes

It sounds to me as though something (maybe not needle, maybe very fine hair like on chumbas) is still in there. Not enough for the body to reject/cause infection, but enough to be sensitive. Have you tried the usual digging with a needle?

Thanks Fiona. I think you could be correct. I would try the digging but there's nothing at at to see.

I googled poultice/cactus hairs and there are loads of results but this one seems to cover the most frequent type mentioned: bread and milk, mainly!
http://ehealthforum.com/health/topic109054.html

Some of them are so fine, they're virtually impossible to see with the naked eye.
The same ones can easily end up in your skin without you actually touching the plant, as they can often be windborne in close vicinity of the cacti at certain times of the year.

Get yourself some nail varnish and spread some over the area that is giving you trouble.Let it set up for a day or so and then gently pull the varnish off.If there are any needles in your skin then they should come out with the varnish. If you get any larger catcus needles in your arms /legs etc then use a comb that you comb your hair with and then slide it up your skin and through the needles and they will come right out. We get many many different kinds of catcus here in Arizona and use these methods all the time.Hope it helps.

That nail varnish one sounds good. Here, the big prickles aren't too difficult, because they're obvious. Chumba is a different beast - those fine hairs !

Try soaking your finger in soapy water, it will hopefully float out, if not just open the area a little with a sterilized needle ie hold the needle over a flame to sterilize it and soak again

Thank you so much to all of you. I will certainly try the nail varnish. I will also make a note of the other remedies just in case

Some cacti needles are seriously unpleasant, some are hollow and therefore allow air to get to the nerves, highly unpleasant!

I always throughly wash cactus spine injury areas with 100% alcohol, some have nasty substance in them.