As some of the comments suggest, pursing can be ambiguous referring to outward/inward lip rolling. This following reference explains more, and explains the related body language signals (though, curiously, it all but omits the "pout").
Remorse addresses the speaker's moral sense of personal guilt. It is directed inward, a gnawing feeling of distress over one's own responsibility for one's own grave error—in many cases a sense of having sinned; while regret is directed outward—an unmoralized feeling of distress over the unhappy consequences of an act which may have been performed (or omitted) by anyone. So remorse can be ...
FRA conducted a literature review to determine the effectiveness rate of inward- and outward-facing recording devices but “was unable to determine an appropriate rate.” According to FRA, the benefits ...
Possible Duplicate: When is it necessary to use a hyphen in writing a compound word? To hyphenate or not? Which one is correct? The normal vector we mean is the inward-pointing normal. The normal ...
This word does not start with S but it certainly carries the meaning you are looking for. It is a verb that can be used both transitively and intransitively: Incurvate (or incurve) to curve or cause to curve inwards (Collins) e.g. Gravity incurvates the rays. The body incurvates a little at the back. (finedictionary.com) It's a start. Maybe looking up its synonyms might help you find your s word.
To change the inside TFD person (inward character, perceptions, or feelings) so the outside TFD person changes too (On or to the outer or external side). Prior external influences are no more. As in: 'He would have to tear himself from the inside out to find the truth.' 'In rehab, they changed me from the inside out.'