Force = (Mass x Impact speed) / Impact Time.... F = MV / t
Mass = 11.5 stone = 73kg
Some of your mass was taken by your knee, so I'll assume that only a third was taken through your nose (to be generous)!! So the correct mass value, m = 73 x 1/3 = 24.33kg.
Imapct speed, V = sqr root (2 x a x S)
Acceleration, a = gravity, 9.81m/s
Height (Disatnce fallen, S) = 4' 10" (allowing for 5 inches of head above your nose) = 1.47m
Therefore Impact speed, V = 5.37m/s
The time taken for your momentum to be abosrbed through your front crumple zone (fleshy bit of nose) was probably quite small, say about 0.1 seconds. t = 0.1seconds
So, F = (24.33 x 5.37) / 0.1 = 1307N
This was spread through the surface area of you squashed nose, which based on my nose is probably about 1/2 a square inch.
Which makes it about 2614 Newtons / square inch which is equal to about 587 lbs per square inch!! Congratulations on not breaking your nose!!!!
Please do not respond to this telling me taht it's all wrong - this answer is based on basic principles, outrageous assumptions, and a couple of quick calculations including excessive rounding and guesstimation. Perfectly good for a fact to tell your mate over a pint, but clearly not something to rely upon in a court of law!!!
If you really want to know the answer, we'd have to get you into a wind tunnel to work out your drag coefficients etc in order to work out your actual fall speed, we'd have to findo out the compressive resistance of your nose, your weight distribution and millions of other factors!
Apologies if I made any stupid mathematical mistakes, I did it in a bit of a rush! And please, no jokes about me being a muppit - I am really very clever.