Indented ileostomy

Second time with an ileostomy, had cancer of rectum with many complications including recto- vaginal fistula. In March I received my second ileostomy, looks to be permanent. I am trying to learn as much as possible.Iwould like to know what blockage is like. I also noticed this morning when I changed mt bag that my stoma looked like it was sinking in. What does that mean, if anything. Thanks in advance for any help!!!!! Nice to be among you all.....ila