Hello !!
You can go for vegan source of
Vitamin D like soya milk , mushrooms , cheese(cheddar) , these days u also get vitamin d fortified greek yogurt. By the time you can start Tab. Uprise D3 one tablet once a week for 2months to replenish your vitamin D levels . Get plenty of morning sunlight if possible. And Importantly , exercise !!
Next Steps
Vitamin D supplementation , diet modification , sunlight !!