Should I get a lice treatment if I was around a child for two days who had them, but had already received their first treatment?

No, it is not necessary to undergo treatment for lice in this situation. Lice treatment is only needed for individuals who are found to have lice. Therefore, if you were in contact with a child who had lice but had already received treatment, there is no need for you to undergo treatment as well. You can rest assured that you do not need to worry about it.