Welcome to the forum. Im sorry to hear you have problems at your barn.
Your horse could have done almost anything and came up lame, from buck and twist his leg the wrong way, to having a stone bruise, to banging his foot or leg getting up from a rest.
It is highly unlikely someone in your barn would do such a terrible thing to you because they don't like you. Yes, horses have been lamed on occassion, but not because of a barn tiff.
Horses who have been lamed on purpose are usually horses who are top competitors, and unfortunately some very unintelligent people don't like to be beat fair and square.
If you are truly that worried that you would even think someone in your barn would intentionally harm your horse you need to move immediately. How can you even enjoy owning a horse when you are with people who do not care to be your friends. It must be very difficult. I feel sorry for you and your horse.
Please don't be afraid to call your vet if your horse is sore. Don't let barn gossip and banter dictate to you whether you should treat his injury. Horses do not fake swelling or soreness. It indicates you need a vets advice.