What protein-filled snacks are good alternatives to nuts?

You can probably try out roasted soya beans.

You can try boiled eggs, canned tuna, hemp seed protein power, soy protein powder, and many non nut based complete protein snacks you can eat. Try this delicious green smoothie shake (add in hemp seed protein) during your rugby and long workouts and it also hydrates you. Hopefully this helps :-)

That's a hard one! Can you still eat seeds, even though you can't have nuts? Sunflower seeds, pumpkin seeds, and sesame seeds are great. Sunflower butter is also delicious. Here's a nut-free granola bar recipe that includes seeds: http://www.thepaleomom.com/2013/02/nut-free-paleo-chewy-granola-bars.html. Another food you may not have considered is gelatin (specifically the ind from grass-fed cows) is very high in protein. There are recipes online to make protein bars/shakes using it. Here's one: http://butternutrition.com/chocolate-pudding-protein-bars/. I second the idea of hard-boiled eggs (someone else mentioned that one). Also, nitrate-free lunch meats could work, depending on how long you'll be keeping them out.  Finally, there are some Paleo snacks that are nut free, and it might be worth buying a box of those to have on hand. Example: https://thrivemarket.com/tanka-bar-natural-buffalo-and-cranberry-bar-slow-smoked-original?fee=1&fep=2607&utm_source=google&utm_medium=pla&utm_campaign=Default+Category%2CSelects%2CFood+%3E+Snacks+%3E+Jerky%2CFood&utm_content=897737001048-Buffalo+Meat+and+Cranberry+Bites&gclid=Cj0KEQjwoYi4BRDF_PHHu6rI7NMBEiQAKZ-JuOwtJJucTsj436islUOe0wxvuDStnBN5gB6YAtsxzOAaAp698P8HAQ. I try to make sure my kids' lunches are high protein, but the schools often don't allow nuts. It can be tricky!!

Beef Jerky Protein Bars (there are some by quest and mission)Roasted edamame Bananas (would be good for endurance sports likerugby) Any kind of glucose sport packet, instant energy provider and no refrigeration needed.

I really know nothing about it, but there is packaged milk in small cartons now that doesn't require refrigeration. Milk is a whole protien. 

Jerky is at the top of my list along with high quality protein bars.Read: http://fitgalri.com/blog/lean-protein-snacks