I had a kidney stone on christmas it was tested and it was bc of oxaltes I was put on special diet, is this serious? Is this hypoxaluria?

Many paths to CaOx. While your stones are made of calcium oxalate, the cause for why you make stones is best assessed by undergoing a 24 hour urine collection. This, paired with blood work, can help to show why you make stones. The answer could be elevated urinary oxalates....Or not. Other causes include low levels of citrate or magnesium in your diet (easily replaced), low urine output or high urinary calcium.
Evil Oxalates. Calcium oxalate is the most common composition for stones. Contrary to popular belief, you should continue to take calcium (eat cheese, drink milk, take a multivitamin). Avoiding oxalates is key (ice tea, spinach, kale, chocolate). The excess oxalates are in my opinion to blame. High oxalate containing foods can be food via the internet. Limited quantities of these and fluid in take are best.
Oxalate stones. Calcium oxalate forms over 70 percent of stones in humans. A reduced oxalate diet helps. So does a deliberate intake of extra citrate daily, achieved from orange juice 8 oz twice daily plus 4 tablespoons of ReaLemon extract daily. And drink 3-4 liters fluid per day, limit salt, and limit meats. Ask doc for blood and 24 hour urine testing for stone profile (Quest Lab, Litholink Lab, or Lab Corp)