Can't use any tool

If you want to draw over your sketch to make a logo Illustrator is the correct application for that since it can help you create a proper vector-based logo based on your image. Far too many people make the mistake of designing a logo within Photoshop and then are stuck when they suddenly need to provide vector-based artwork to someone or they just simply need to make the logo bigger without losing any image quality.

Once your PNG image is placed in a new Illustrator document and positioned on the page how you want it, open the Layers palette. You can lock your image into place using one of two methods. One option is creating a new layer above the first layer and then locking the first layer. Do that by clicking the blank square to the right of the eyeball. You can also lock individual objects within a layer. Just click the drop down arrow to the left of the layer name. It will reveal a list of objects in that layer. You can lock/unlock specific objects in the layer, move objects up or down to change their stacking order as well as delete objects that aren't needed. Lots of things can be done just within that palette.

When your image is locked in place you can use a variety of tools to draw over the top of it. The Pen Tool and Paintbrush Tool are the most commonly used tools to vectorize hand-drawn artwork.

It's probably not on every tool you select, but on many. If you want to use the brush tool on that image, then you need brushes. What you want to do: Create a new file in Illustrator and then Place that PNG.

What do you want to do with the image?

Illustrator is a vector editing application.

For image editing Photoshop is the right application.