Fairly sure it's the same ankle he twisted against Bournemouth.
If you twist an ankle it can sometimes swell up again when you put it under too much pressure, for a little while even if it seems properly healed otherwise. Hopefully that's all that happened and he's not re-injured it.
I thought he looked good in the first half, a little rusty as you might expect given he's missed a few matches, but some lovely passes and runs into the box, held the width on the left well and largely did what Pep likes him to do in terms of maintaining possession and controlling the tempo.
Thought he seemed off it as his second half performance went on, presumably due to pain/mobility issues in that ankle.