Yes! You can use BB creams as concealers but BB creams may not be as effective as a concealer for tougher spots.
A Concealer is mainly used to conceal and hide tough-to-hide imperfections. They can help cover eye lines, wrinkles, under-eye bags, dark circles, blemishes, and other skin impurities.
A BB cream, aka ‘beauty balm’, ‘blemish balm’ or ‘blemish base’, is designed to cover and conceal minor imperfections with a light finish.
The main distinction between BB creams and concealers is that BB creams contain skin-care ingredients that are meant to help moisturize, hydrate and protect your skin. BB creams are supposed to make the skin look better and more energized. They are sometimes referred to as tinted moisturizers because they are essentially skincare products that are designed to blend into your skin.
Concealers are usually not considered skin-care products. Although some do have skincare features, the features are limited.  They have a thicker consistency than a BB cream and their main function is to cover blemishes or skin imperfections with deep colors that are hard to cover.