Flynn could still face charges, he hawked for Turkey, without telling the government, while working for Trump.
Judge Sullivan wanted to see him again...
and...
If Sally Yates is the new AG, that will be interesting. She was the person that warned Trump that Flynn was compromised. It still took 17 days for Trump to fire him, only after it became public that Flynn was tainted.
In what types of cases can the president not grant pardons?
One limitation to the president's power to grant pardons is "in cases of impeachment." This means that the president cannot use a pardon to stop an officeholder from being impeached, or to undo the effects of an impeachment and conviction.

DO SOMETHING!