.Everyone should examine any strategies shared here thoroughly to know if they will suit their body strength so that there will not be any shoulder injury in this challenge.
A body that's has alot of fats and not used to burning this fats will definitely feel alot of pains than usual while burning those fats.
Moreover, it don't have to be physically fat to possess some body fat levels it's called "Skinny Fat" that's why its advice to always check your BMI (Body mass Index ) .
Did some little practice 3years back when I was starting to learn how to code although I'm not more of a python dev again

x=int(input("Your weight "))
b= (float(input("Your height ")))**2
p=(x/b)
print(p)
if p < 18.5 :
print("under weight")
elif 18.5 <=p < 25:
print("Normal")
elif 25 <= p< 29 :
print("Over weight")
elif p >= 30 :
print("Obesity")
There are standard calculators on net that archives this currently you can check
https://www.nasm.org/resources/bmi-calculatorBack to the arm pain , the arm pain is not going to be the only pain but also your lower arm,lower chest, eight and left side of your abdomen, the muscles covering the back pat of your tibia shaft and lot more. The only way one could eventually avoid this is by taking rest some days to prevent being overwhelmed by the pain or you could try some other exercise that are of less effort or probably reducing the pushups for some period will do
Don't worry keep up the work $100k will be achieved soon...