I have noticed a sweet burning smell coming from my car after a bit of having the heat on. It seems like it’s a coolant leak, but I haven’t noticed anything leaking underneath my car. Since my coolant is low would I be fine just topping it off until I am able to get it repaired or should I try to get it fixed as soon as possible?

I drive a 2013 VW Jetta 2.5L SE.