On Monday afternoon, my 5 month old filly had her halter on and she snagged it on a fence for a few moments. I saw her head jerking back and forth to free herself and she finally got it released after a few seconds. Since then, she holds her head down, isn't her normal playful self and is kind of mopey. She is eating however I'm not sure how much because she doesn't like to lift her head into the feeder. I put some hay on the mat for her and she will eat that. She may be just bruised or sore, but how long should I let it go before I call the vet?