If you can take a picture and save it on the cloud, then attach a link, then we can see it. This will help a lot, but I will take an educated guess.
First problem, plastic doesn't fill the mold when you inject it. It sound like you don't have vents to let the air out ahead of the plastic. When you inject it forms a seal and to get the room available for the plastic you need air escape vents. The big guys that inject plastic call this sprues and it is trimmed off after the items cools. Small items may need only very tiny vents but larger items will need either more or larger vents. If your mold are silicone, just use a razor knife to cut some small channels. If your mold is VAC 50, you will need to do it with a Dremel tool.
The second problem tells me you are probably injecting a larger item. Denting after the pour is the result of the plastic shrinking as it cools. One way to deal with this is to create a mold with a reservoir from which the cooling plastic can draw. At about 2:35 into the following video you will see the plastic reservoir that leads to each of the lures which helps provide a place to draw from.
http://www.makelure.com/store/pg/54-How ... yPhoto/23/ In the following video, it is an open pour design, but you can still see the extra reservoir on top to allow for the cooling plastic to draw.
http://www.makelure.com/store/pg/54-How ... yPhoto/37/If the dents are not too large, you can often eliminate them by holding pressure on your injector a few seconds longer at the end of the pour.
I hope I have made this clear, and good luck on your pour/injection.