In Oliver Twist, who took care of Oliver when he was shot?

Readers should begin looking for this answer in chapter 22. This is the chapter that sees Sikes forcing Oliver to help with a robbery. Oliver figures that he can stop the robbery by somehow waking the family. Unfortunately for Oliver, this doesn't work. Oliver is shot, and Sikes is forced to pull Oliver back out of the house and to run off with him.
Unfortunately for readers, the next chapter doesn't tell us what happened. Toby recounts the events to Fagin at the end of chapter 25, and readers realize that Sikes just left Oliver in a ditch. Readers then have to wait until chapter 28 to read about Oliver. Oliver is in great pain, but he manages to get himself back to the house he was just shot in. He knocks on the door, and Mr. Giles carries Oliver to a bed.

"Not now, for the world," replied the young lady. "Poor fellow! Oh! treat him kindly, Giles for my sake!"
The old servant looked up at the speaker, as she turned away, with a glance as proud and admiring as if she had been his own child. Then, bending over Oliver, he helped to carry him upstairs, with the care and solicitude of a woman.

The next chapter then makes it clear that Mrs. Maylie and Rose tended to Oliver for the remainder of the night. A doctor does show up the next morning, but readers are not told specifics about whether or not he takes any action beyond what the two women have already done.

At length he returned; and in reply to an anxious inquiry after his patient; looked very mysterious, and closed the door, carefully.
"This is a very extraordinary thing, Mrs. Maylie," said the doctor, standing with his back to the door, as if to keep it shut.
"He is not in danger, I hope?" said the old lady.
"Why, that would not be an extraordinary thing, under the circumstances," replied the doctor; "though I don't think he is."

Fagin forces Oliver to help the gang with a burglary. Sikes pushes Oliver through a small window and tells him to unlock the door. Once inside, however, Oliver tries to alert the family—only to be noticed by two employees of the house. Oliver is subsequently shot in the men's defense of the house. Sikes carries Oliver away from the house, but then abandons him in a ditch.
Oliver wakes up the next morning weak from his injury. He walks forward in a daze, and he ends up at the same house the gang tried to rob. He knocks on the door, and the women of the house order the robber to be brought upstairs and tended to. Mrs. Maylie and her niece Miss Rose Maylie keep Oliver in their home and tend to him, along with the help of Dr. Losborne, who convinces others in the house that Oliver is innocent.