as i said, dpi has really absolutely nothing to do with ingame textures. dpi means "dots per inch" which translates to pixels drawn per inch (~2.5 cm). this is just a number stored in your file and does in no way affect the image data.

for ingame textures all that counts is the resolution, which is width and height. normal textures have a size of 128x128 to 1024x1024 pixels. higher resolution means (mostly) higher quality, but lower performance. it's a matter of experience which textures you choose for a specific job.

scaling the texture ingame would be a pendant to the dpi stuff, something like texels per quant. but this is mostly irrelevant, as most designers just scale their textures so that they look good.