My dogs ear is swollen?

I have a very small fluffy dog (maltipoo). The tips of her ear is swollen. It is not red or bothering her at all. It does not weigh down her head or cause her to act differently. When I touch it, it doesn't even bother her. It isn't even squishy. But it is more swollen than it was in the past week and I am worried about it. What could be the problem?