Morning
Warm welcome to the group, not a club anyone wanted to join :-/
Heel Pain / Numbness seems to be a 'thing' with hormone therapy tablets whether that be Tamoxifen, Letrozole, Anastrozole etc
Several ladies here have had this or mentioned it but doctors seem reluctant to confirm the two are linked. The pain seems to be exactly as what is described in Plantar Fasciitis (policemans foot) from when they walked the beat, or rather stood still a lot.
First off you could get some 'Gel' type heel inserts until you can ease this. Some have found stretching exercises help. First thing in the morning raise and point your toes towards your chest to stretch out your calf muscles a few times - Another way folks have found helps is to stand on the bottom step of your stairs (or you could use a block or something like a chopping board between 3 - 5 cm thick with your heels overhanging the back edge and gradually lower yourself to stretch the plantar ligament that runs from your heel to the ball of your foot.
Another easy do'able method is the Can Roll, Tennis Ball or Frozen Water Bottle exercise - see image.
If after doing this for a while it doesn't seem to be helping (easing this can take quite a while) you could get a cortisone injection but that tends to be a last resort. Mostly after a couple of months this seems to disappear on it's own ?
Another possible fix is to change the brand of Letrozole, there are around 6 brands of generic letrozole - most find one that suits them over the others and try to stick with it. Although this heel issue seems to stem from lack of oestrogen rather than the 'fillers' used to bulk up the tablets.
If you type plantar fasciitis into the groups search bar it will bring up previous messages about this - make sure you spell it correctly though 
Hope this is of some help for now, take care, G n' J
