Weird toenail

So my 19 month old has had this spot on her toenail for a few months now. It hasnt moved down the nail any further than this.. it kinda smells almost yeasty/buttery?? (Her other foot doesnt not smell! And i washed her feet and it smelled odd by this nail.

But everything ive looked up says brown spots under nails are cancer. Im kinda freaking out. Anyone know what this might be or does their toddler have this?!

Note- ill probably be calling the pediatrician about it since her next appointment isnt until she is 2. But i just wanted to see if anyone else has seen this before.