I suggest you get a concealer as soon as you can but in the meantime it's best to use a liquid foundation. Any other form of foundation won't help cover up the scarrs well enough. The liquid foundation should be - like the concealer - a few shades lighter than your skin. Dab it on and start blending but don't completely blend it in otherwise your marks/scarrs will still be visible. After doing that use a a very tiny amount of darker foundation over it. This should help subsitute concealer for the timebeing.